Re: CVS commit: src/sys/dev/usb

[Nick Hudson <nick.hudson%gmx.co.uk@localhost>]

On 29/09/2025 17:31, Nick Hudson wrote:
> On 29/09/2025 15:21, Rin Okuyama wrote:
> > Module Name:    src
> > Committed By:    rin
> > Date:        Mon Sep 29 14:21:46 UTC 2025
> >
> > Modified Files:
> >     src/sys/dev/usb: ehci.c
> >
> > Log Message:
> > ehci: usb_syncmem against qtd **after** KASSERT for that qtd
> >
> > Otherwise, we end up with stale data for DIAGNOSTIC kernel.
> >
> > Fix device-probe failures discussed in PR kern/58730 for me.
>
> This doesn't make sense to me.
>
>
> The TD shouldn't be accessed by hardware at this point (unless something 
> is using the transfer incorrectly, e.g. twice) and the KASSERT is there 
> to ensure correct protocol - the status stage of the transfer should 
> always have toggle set.
>
> It suggests to me that the cache operation is not writing back and 
> invalidating, and therefore losing the TD configuration.

To be a little clearer...

it suggests the writeback doesn't happen before an invalidation so the 
toggle bit being set doesn't make it to memory.

The BUS_DMASYNC_PREREAD should ensure the writeback part.

Nick